Network timeouts over WAN
Posted on 1998-06-19
We have a dedicated 56K line to an ISP using a Cisco router and a Motorola CSU/DSU. We seem to be having a lot of timeout problems with traffic crossing the WAN. It seems to occur only with large blocks of data (files, mail messages, etc.) of at least 100K. It may be that any size is
succeptable, but that it shows up easier with larger transfers.
For example, I set up an FTP server on our site and telneted into a machine at the ISP site. I tried uploading a file to our server (about a 1MB file). There is a 100% failure rate with this test. The connection is always
established with no trouble (as far as I know anyway), then proceeds along happily until the transmission suddenly stops (forever) until the TCP timeout.
Note, this is NOT isolated to FTP. Our mail server has trouble receiving large messages as well. The server is running NT Server 4.0.
I thought originally that there may be a problem with that particular machine, so I set up a slightly faster machine with a better NIC with the same results. Testing with other machines running Internet Explorer "seem" to have no trouble with web pages. However, though I am able to download files, there does seem to be an unusually high timeout rate here as well.
Traffic on the LAN seems to have no problem whatsoever.
What do you think could be the problem?